Dyeing processes utilizing oxidation dye such as phenylenediamines and aminophenols are frequently used in dyeing of keratin fibers, specifically human hairs and the like, by utilizing the advantages that dyeing in various color tones is possible and the duration is long, as well as that the dyeing time is short, and the like. Hydrogen peroxide has been conventionally used for the color development of oxidation dyes. However, hydrogen peroxide has a strong irritant property, and hairs and scalps and the like are damaged by using hydrogen peroxide. In order to overcome such problem, use of an oxidase instead of hydrogen peroxide has been attempted (for example, see Patent Documents 1 to 3).